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Abstract-During the last few years there has been an intensification of interest in the fatigue performance of steel reinforcement bars in concrete structures. Although fatigue has not proved to be a problem to date, loading cycles are becoming increasingly severe so that the margin of reserve strength is progressively being reduced.In this paper the main parameters associated with fatigue of reinforcement are reviewed with particular attention given to conditions related to highway bridges. Fatigue testing can be either axial in air or by bending of reinforced concrete beams. The latter is experimentally less convenient but simulates more closely the service environment. Endurances can be influenced by type of steel, geometry and size of the bars, nature of the loading cycle, welding and presence of corrosion. The relative behaviour of butt welded joints is considered and it is shown that the reduction in fatigue strength commonly attributed to flaws and to the stress concentrations associated with welds does not always occur for bending fatigue of reinforced concrete beams.

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